There is an urgent need for a new microbicide that may be used as a vaginal application under female control, to halt the spread of sexually transmitted diseases (STD's). Of greatest concern is the rapid spread of HIV into the heterosexual population, in which females appear to be more susceptible to the infection. Vaginal barrier creams, which are under female control contain Nonoxynol 9 (N-9), a nonionic surfactant that is the most frequently used spermicide both nationally and internationally. Indeed, N-9 is the only FDA-approved spermicide available in the U.S.A. Studies with N-9 over the past two decades have shown that it is bacteriocidal for Neisseria gonorrhea, Trepenoma pallidum and Chlamydia trachomatis. More recently N-9 has been shown to have virucidal activity against HIV when tested in vitro. Despite the evidence that N 9 is a microbicide in vitro, there are concerns regarding it's in vivo use. These have arisen because of reports that N-9 may cause local trauma to genital tissues. Thus, there is an urgent need for microbicides that do not disrupt the delicate epithelia of the reproductive tract and colon. C31G is a compound with broad spectrum antibacterial, antiviral and antifungal activity with potential to provide protection against STDs. Interestingly, C31G displays differential toxicity. Effects on microbes and yeasts are detected at a MIC lesser 0.001% (minimum concentration of drug that inhibits bacterial growth) while effects on mammalian spermatozoa are seen at least one order of magnitude higher (0.01%), and it is considerably les toxic to human somatic cells as compared with N-9. In project #6, we will evaluate new formulae and formulations of C31G for cytotoxicity against human epithelial somatic cells and spermatozoa. This will be done using conventional cytotoxicity assays, at two pH levels (5.5 and 7.0) to reflect the environment of the vagina before and after sexual intercourse, and in the presence of cervical mucus and spermatozoa. Once potential microbicidal formulations have been identified, the assays will be refined by the use of microfabricated channels in 'chips'. Using these chips in conjunction with cells labelled with fluorescent probes, the viability of epithelial and sperm cells will be evaluated by means of fluorescent microscopy as well as evaluating the effects on two pathogens, Neisseria gonorrheae and Chlamydia trachomatis int he presence of cervical mucus and seminal plasma. When these studies have been completed, a miniaturized, three dimensional replica of the human reproductive tract, etched in glass will be utilized in order to more closely represent the dynamics in vivo, and the components of the study will be evaluated in this structure.